Good game! Although, the progression feels lacking (after wave 20 there is no new content or challenge, so the game should just finish at around wave 30) and doppelganger tiles are bugged: in some games, enemies keep attacking them forever, even after killing spawned clones. And it feels weird not being able to remove the previously placed tiles. Fast forwarding would be greatly appreciated too.
UPD: Alright, there is actually a new enemy type at wave 50. But I wish it appeared a lot sooner, or there was some kind of indication of this event